Two separate teams of researchers say they have sidestepped thecloning method and reprogrammed mature human cells into a primordial,embryonic-like state. Those cells were then transformed into other tissue types, such as heart cells. The long-term hope is that such freshly-created tissue may, for example, be used to heal a heart-attack patient. Unlike cloning, "the wonderful thing about this approach is that it's easy."

There are several limitations to the current approach. For now, both teams had to use dangerous viruses to effectively transport the genes into the cell, which could have deadly consequences if it was immediately applied to humans. Dr. Yamanaka and others say they are testing other viruses in the hopes of finding a non-harmful one.

And before the reprogramming technique can be applied to human patients, it needs to be tested on large animal models to ensure that it's safe and effective.

Still, the latest results are a big step up from similar breakthroughs in mice, separately reported this summer by Dr. Yamanaka's group and two other research teams in the U.S. The Kyoto team reported that embryonic-like cells developed with the new technique could even help form a new mouse -- a gold-standard test for the viability of the created tissue.